1. Field of the Invention
The present invention relates to a method of double-sided printing, in effect, on opposite or both surfaces of a layer on a multi-layered foil laminate. Moreover, the invention is also directed to the provision of a novel multi-layered foil laminate having at least one layer, preferably an exterior layer which is constituted of a plastic film material, and which is provided with printing on both surfaces of the layer.
The utilization of foil laminates which possess an external surface which is imprinted with various legends and indicia, and whereby the foil laminate may be utilized, among numerous other physical applications, as lid stock for plastic packages, such as the so-called "blister packages" of the injection molded type, is well-known in the packaging technology.
2. Discussion of the Prior Art
In many instances, the externally arranged layer of the lid or cover-forming foil laminate; in essence, the layer having a surface facing the outside of the package, may be provided with suitable printing. For example such printing may consist of indicia or legends identifying the manufacturer, the manufacturer's logo and miscellaneous information and decorative and advertising indicia identifying the product in the package, and include suitable variable technical information, such as expiration dates, lot numbers and other dataspecific to the packaged product.
Basically, such multi-layered foil laminates in the form of webs which are employed for lid stock purposes include outer layers of suitable plastic film material adhesively fastened to both sides or opposite surfaces of a foil web. Such a foil web is ordinarily constituted of a suitable metallic material, which may be aluminum or the like, and wherein one of the plastic film material layers is adapted to be adhesively secured, such as by means of heat sealing or the like, to the injection- molded material of the plastic container or package whose contents it is adapted to seal therein. Frequently, blister packages or similar plastic containers which have covers in the shape of foil laminates applied thereto are subjected to potentially damaging temperature and/or environmental conditions. This may be the case when the entire package is subjected to sterilization, as in the instance when the product housed therein is intended to be employed in a medical capacity; for example, a product such as a contact lens which is adapted to be packed in a sterile saline solution and sealed in a compartment or cavity of the package.
It is essential to be able to ensure that the printing which is normally provided on the exterior of the package will safely withstand these above-mentioned conditions without either being completely obliterated or even only rendered partially illegible. Consequently, it is an important aspect that suitable kinds of printing be employed which will not only remain stable under such adverse physical conditions, but which will also avoid any deleterious effects to be imparted thereto. Thus, for instance, when the outer plastic film material layer at one side of the laminate is constituted so as to possess a printable and generally transparent nature; for instance, such as a polyester film. Currently employed types of printing are not sufficiently adequate to meet the stringent demands of industry. Thus, the utilization of laser printing does not always provide for a satisfactory printing result, while hot stamp printing produces impressions in the laminate which may adversely affect the mechanical sealing properties thereof with regard to the underlying surface portions of the package or container to which the laminate is to be heat sealed or bonded.